Immunogenic peptides, containing epitopes recognized by T helper cells, have been found to be useful in inducing immune responses. The use of helper peptides to enhance antibody responses against particular determinants is described for instance in Hervas-Stubbs, et al., Vaccine 12:867-871 (1994).
Although allele-specific polymorphic residues that line the peptide binding pockets of MHC alleles tend to endow each allele with the capacity to bind a unique set of peptides, there are instances in which a given peptide has been shown to bind to more than one MHC allele. For example, several investigators reported degenerate binding and/or recognition of certain epitopes in the context of multiple DR types, leading to the concept that certain peptides might represent “universal” epitopes (Busch, et al., Int. Immunol. 2:443-451 (1990); Panina-Bordignon, et al., Eur. J. Immunol. 19:2237-2242 (1989); Sinigaglia, et al., Nature 336:778-780 (1988); O'Sullivan, et al., J. Immunol. 147:2663-2669 (1991); Roache, et al., J. Immunol. 144:1849-1856 (1991); Hill, et al., J. Immunol. 147:189-197 (1991)). Pan-DR binding peptides have been described in, for example, U.S. Pat. No. 6,413,935; WO 95/07707; WO/2005/120563; and Alexander, et al., Immunity 1:751-761 (1994). These peptides have been shown to help in the generation of various immune responses against antigens.